/*
 * Copyright (c) 2017-present, CV4J Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.cv4j.core.filters;

import com.cv4j.core.datamodel.ImageProcessor;

import java.util.Optional;

/**
 * 伽马滤波器
 *
 * @author dev
 * @date 2021/07/22
 */
public class GammaFilter extends BaseFilter {
    private int[] lut;
    private double gamma;

    /**
     * 伽马滤波器
     */
    public GammaFilter() {
        this.lut = new int[256];
        this.gamma = 0.5;
    }

    /**
     * 做的过滤器
     *
     * @param src src
     * @return {@link ImageProcessor}
     */
    @Override
    public Optional<ImageProcessor> doFilter(ImageProcessor src) {
        // setup LUT
        setupGammaLut();
        int index = 0;
        for (int row = 0; row < height; row++) {
            int tr = 0;
            int tg = 0;
            int tb = 0;
            for (int col = 0; col < width; col++) {
                index = row * width + col;
                tr = RED[index] & 0xff;
                tg = GREED[index] & 0xff;
                tb = BLUE[index] & 0xff;

                // LUT search
                RED[index] = (byte) lut[tr];
                GREED[index] = (byte) lut[tg];
                BLUE[index] = (byte) lut[tb];
            }
        }
        return Optional.ofNullable(src);
    }

    /**
     * 设置伽马附近地区
     */
    private void setupGammaLut() {
        for (int i = 0; i < 256; i++) {
            lut[i] = (int) (Math.exp(Math.log(i / 255.0) * gamma) * 255.0);
        }
    }
}
